Abstract:

A blood pump apparatus comprises a housing, a centrifugal pump section
including an impeller and rotating inside the housing to feed a fluid by
a centrifugal force, an impeller rotational torque generation section for
attracting thereto said impeller and rotating said impeller; and a
plurality of grooves for hydrodynamic bearing provided on an inner
surface of said housing at a side of said impeller rotational torque
generation section, each of the grooves for hydrodynamic bearing having a
first side and a second side both extending from a periphery of said
portion in which a groove for hydrodynamic bearing is formed toward a
central side thereof and opposed to each other, a third side connecting
one end of said first side and one end of said second side to each other,
and a fourth side connecting said other end of said first side and said
other end of said second side to each other; said first side and said
second side are formed as a circular arc respectively in such a way that
centers of said circular arcs are different from each other.

Claims:

1. A blood pump apparatus comprising:a housing having a blood inlet port
and a blood outlet port;a pump section including an impeller having a
magnetic material and rotating in said housing to feed blood; andan
impeller rotational torque generation section for attracting thereto said
impeller of said pump section and rotating said impeller,wherein said
pump section further comprises a groove for hydrodynamic bearing provided
on an inner surface of said housing at a side of said impeller rotational
torque generation section or a surface of said impeller at said side of
said impeller rotational torque generation section,said impeller being
rotated without contacting said housing,wherein said pump section further
comprises a sensor for measuring a position of said impeller when said
impeller is rotated without contacting said housing by a hydrodynamic
pressure generated by said groove for hydrodynamic bearing.

2. A blood pump apparatus according to claim 1, further comprising a
permanent magnet attracting said magnetic material of said impeller or a
second magnetic material of said impeller provided separately from said
magnetic material in a direction opposite to a direction in which said
impeller is attracted by said impeller rotational torque generation
section.

3. A blood pump apparatus according to claim 2, further comprising a
second groove for hydrodynamic bearing provided on a permanent
magnet-side inner surface of said housing or said permanent magnet-side
surface of said impeller.

4. A blood pump apparatus according to claim 1, wherein said sensor serves
as a means for measuring a levitation distance of said impeller inside
said housing.

5. A blood pump apparatus according to claim 1, wherein the number of said
sensors is at least three in such a way that said sensors at equiangular
intervals around an axis of said impeller.

6. A blood pump apparatus according to claim 1, further comprising a blood
viscosity-computing function of computing a blood viscosity by using an
output of said sensor.

7. A blood pump apparatus according to claim 6, wherein said blood
viscosity-computing function includes a function of temporarily
decreasing the number of rotations of said impeller to a predetermined
number of rotations; and a function of detecting a vertical swivel length
of said impeller by using an output of said sensor when the number of
rotations of said impeller has decreased to the predetermined number of
rotations by said function of temporarily decreasing the number of
rotations and computing a blood viscosity by using said detected vertical
swivel length.

8. A blood pump apparatus according to claim 7, wherein said blood
viscosity-computing function has a storing part for storing data of a
relationship between said vertical swivel length of said impeller and
said blood viscosity at said predetermined number of rotations of said
impeller or a viscosity-computing equation obtained from said data of
said relationship; and a viscosity-computing function for computing said
blood viscosity from data of said vertical swivel length obtained by said
output of said sensor and said data of said relationship between said
vertical swivel length of said impeller and said blood viscosity stored
by said storing part or said viscosity-computing equation.

9. A blood pump apparatus according to claim 1, wherein said impeller
rotational torque generation section has a rotor having a magnet for
attracting thereto a first magnetic material of said impeller and a motor
for rotating said rotor.

10. A blood pump apparatus according to claim 1, wherein said impeller
rotational torque generation section has a plurality of stator coils,
disposed circumferentially, for attracting thereto said magnetic material
of said impeller and rotating said impeller.

11. A blood pump apparatus according to claim 1, wherein a plurality of
grooves for hydrodynamic bearing is formed on said portion in which a
groove for hydrodynamic bearing is formed;each of said grooves for
hydrodynamic bearing has a first side and a second side both extending
from a periphery of said portion in which a groove for hydrodynamic
bearing is formed toward a central side thereof and opposed to each
other, a third side connecting one end of said first side and one end of
said second side to each other, and a fourth side connecting said other
end of said first side and said other end of said second side to each
other;said first side and said second side are formed as a circular arc
respectively in such a way that centers of said circular arcs are
different from each other;a value relating to a groove depth ratio a
(a=h1/h2) computed from a distance h1 between said impeller and said
housing in said groove for hydrodynamic bearing of said portion in which
a groove for hydrodynamic bearing is formed during a rotation of said
impeller and from a distance h2 between said impeller and said housing in
a groove for hydrodynamic bearing-non-present portion of said portion in
which a groove for hydrodynamic bearing is formed during said rotation of
said impeller is in a range of 1.5 to 2.5; anda value relating to a
groove width ratio s (s=B0/B) computed from a width B0 of a
peripheral portion of each groove for hydrodynamic bearing and a sum B
(B=B0+B1) of said width B0 and a width B1 of a hydrodynamic
bearing groove-non-present portion between peripheral portions of
adjacent grooves for hydrodynamic bearing is in a range of 0.6 to 0.8.

12. A centrifugal blood pump apparatus according to claim 11, wherein said
four corners of said groove for hydrodynamic bearing are rounded.

13. A centrifugal blood pump apparatus according to claim 1, wherein a
plurality of grooves for hydrodynamic bearing is formed on said portion
in which a groove for hydrodynamic bearing is formed;each of said grooves
for hydrodynamic bearing has a first side and a second side both
extending from a periphery of said portion in which a groove for
hydrodynamic bearing is formed toward a central side thereof and opposed
to each other, a third side connecting one end of said first side and one
end of said second side to each other, and a fourth side connecting said
other end of said first side and said other end of said second side to
each other;said first side and said second side are formed as a circular
arc respectively in such a way that centers of said circular arcs are
different from each other; andfour corners composed of said four sides
are rounded.

14. A centrifugal blood pump apparatus according to claim 13, wherein said
third side and said fourth side are formed as a circular arc respectively
in such a way that said circular arcs have a same center and different
radii.

15. A blood pump apparatus comprising:a housing having a blood inlet port
and a blood outlet port;a pump section including an impeller having a
magnetic material and rotating in said housing to feed blood; andan
impeller rotational torque generation section for attracting thereto said
impeller of said pump section and rotating said impeller,wherein said
pump section further comprises a groove for hydrodynamic bearing provided
on an inner surface of said housing at a side of said impeller rotational
torque generation section or a surface of said impeller at said side of
said impeller rotational torque generation section,said impeller being
rotated without contacting said housing,a permanent magnet attracting
said magnetic material of said impeller or a second magnetic material of
said impeller provided separately from said magnetic material in a
direction opposite to a direction in which said impeller is attracted by
said impeller rotational torque generation section,a second groove for
hydrodynamic bearing provided on a permanent magnet-side inner surface of
said housing or said permanent magnet-side surface of said
impeller,wherein said impeller rotational torque generation section has a
plurality of stator coils, disposed circumferentially, for attracting
thereto said magnetic material of said impeller and rotating said
impeller.

16. A blood pump apparatus according to claim 15, wherein a plurality of
grooves for hydrodynamic bearing is formed on said portion in which a
groove for hydrodynamic bearing is formed;each of said grooves for
hydrodynamic bearing has a first side and a second side both extending
from a periphery of said portion in which a groove for hydrodynamic
bearing is formed toward a central side thereof and opposed to each
other, a third side connecting one end of said first side and one end of
said second side to each other, and a fourth side connecting said other
end of said first side and said other end of said second side to each
other;said first side and said second side are formed as a circular arc
respectively in such a way that centers of said circular arcs are
different from each other;a value relating to a groove depth ratio a
(a=h1/h2) computed from a distance h1 between said impeller and said
housing in said groove for hydrodynamic bearing of said portion in which
a groove for hydrodynamic bearing is formed during a rotation of said
impeller and from a distance h2 between said impeller and said housing in
a groove for hydrodynamic bearing-non-present portion of said portion in
which a groove for hydrodynamic bearing is formed during said rotation of
said impeller is in a range of 1.5 to 2.5; anda value relating to a
groove width ratio s (s=B0/B) computed from a width Bo of a
peripheral portion of each groove for hydrodynamic bearing and a sum B
(B=B0+B1) of said width B0 and a width B1 of a hydrodynamic
bearing groove-non-present portion between peripheral portions of
adjacent grooves for hydrodynamic bearing is in a range of 0.6 to 0.8.

17. A centrifugal blood pump apparatus according to claim 16, wherein said
four corners of said groove for hydrodynamic bearing are rounded.

18. A centrifugal blood pump apparatus according to claim 16, wherein a
plurality of grooves for hydrodynamic bearing is formed on said portion
in which a groove for hydrodynamic bearing is formed;each of said grooves
for hydrodynamic bearing has a first side and a second side both
extending from a periphery of said portion in which a groove for
hydrodynamic bearing is formed toward a central side thereof and opposed
to each other, a third side connecting one end of said first side and one
end of said second side to each other, and a fourth side connecting said
other end of said first side and said other end of said second side to
each other;said first side and said second side are formed as a circular
arc respectively in such a way that centers of said circular arcs are
different from each other; andfour corners composed of said four sides
are rounded.

19. A centrifugal blood pump apparatus according to claim 18, wherein said
third side and said fourth side are formed as a circular arc respectively
in such a way that said circular arcs have a same center and different
radii.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application is a divisional of U.S. application Ser. No.
11/087,851 filed on Mar. 24, 2005 and which claims priority to Japanese
Application Nos, 2004-88108 filed on Mar. 24, 2004 and 2004-103573 filed
on Mar. 31, 2004, the entire contents of which are incorporated herein by
reference.

BACKGROUND OF THE PRESENT INVENTION

[0002]In recent medical treatment, centrifugal blood pumps are
increasingly used in artificial heart/lung units for extracorporeal blood
circulation. Centrifugal pumps of the magnetic coupling type wherein a
driving torque from an external motor is transmitted to an impeller
through magnetic coupling are commonly used because the physical
communication between the blood chamber of the pump and the exterior can
be completely excluded and invasion of bacteria can be prevented.

[0003]The turbo-type pump disclosed in Japanese Patent Application
Laid-Open No. 4-91396 (patent document 1) is described below as an
example of the centrifugal blood pump. In the turbo-type pump disclosed
therein, the magnetic coupling is formed by the first permanent magnet
provided at one side of the impeller and the second permanent magnet
opposed to the first permanent magnet through the housing. The rotor on
which the second permanent magnet is mounted is rotated. Thereby the
impeller is attracted toward the rotor with the impeller rotating. The
impeller is spaced at a small interval from the inner surface of the
housing owing to the hydrodynamic bearing effect generated between the
groove for hydrodynamic bearing and the inner surface of the housing.
Thus impeller rotates without contacting the housing.

[0004]In the hydrodynamic bearing pump, the fluid-feeding impeller is kept
out of contact with peripheral surfaces of surrounding parts by a
load-carrying capacity (load-carrying capacity is a term of a bearing and
has dimension of force) generated by the groove for hydrodynamic bearing
and a force resisting to the load-carrying capacity, for example, a
magnetic force. Thereby hemolysis and thrombus are prevented from
occurring.

[0005]The load-carrying capacity varies according to the configuration of
the groove for hydrodynamic bearing. That is, the distance between the
impeller and the surrounding parts varies according to the configuration
of the groove for hydrodynamic bearing. Therefore the designing of the
configuration of the groove for hydrodynamic bearing is important.

[0006]In the conventional groove for hydrodynamic bearing, the principal
object is to increase the load-carrying capacity. Thus a logarithmic
spiral groove is conventionally adopted. However, it is important to
prevent the hemolysis to a high extent in addition to making the
load-carrying capacity high.

[0007]It is a first object of the present invention to provide a
centrifugal blood pump apparatus not of a type of magnetically levitating
an impeller but allowing a rotation of the impeller without substantial
contact between the impeller and a housing by utilizing a groove for
hydrodynamic bearing and preventing occurrence of hemolysis to a high
extent during use.

[0008]In the hydrodynamic bearing pump, the fluid-feeding impeller is kept
out of contact with peripheral surfaces of surrounding parts by a
load-carrying capacity (load-carrying capacity is a term of a bearing and
has dimension of force) generated by the groove for hydrodynamic bearing
and a force resisting to the load-carrying capacity, for example, a
magnetic force. Thereby hemolysis and thrombus are prevented from
occurring.

[0009]The present applicant proposed the centrifugal fluid pump apparatus
as disclosed in U.S. Pat. No. 6,840,735 (patent document 2). The
centrifugal fluid pump apparatus 1 has the control mechanism 6 and the
pump body 5 including the pump section 2 having the impeller 21 rotating
in the housing 20; the rotor 31 having a magnet 33 for attracting the
impeller 21 thereto; a motor 34 for rotating the rotor 31; the
electromagnet 41 for attracting the impeller 21 thereto, the sensor 42
for detecting the position of the impeller 21, and the groove 38 for
hydrodynamic bearing provided on the inner surface of the housing 20. The
control mechanism 6 has the position sensor output monitoring function
56, the electromagnet current monitoring function 57, and the motor
current monitoring function.

[0010]Whether the sensor has a failure is determined by using the position
sensor output monitoring function 56. Whether the electromagnet has a
failure is determined by using by using the electromagnet current
monitoring function 57. The centrifugal fluid pump apparatus 1 further
includes the emergency impeller rotation function that operates when the
failure detection function has detected that the sensor or the
electromagnet has a failure to rotate the impeller 21 by utilizing the
groove 38 for hydrodynamic bearing.

[0011]In the hydrodynamic pressure bearing pump, the impeller is kept out
of contact with the housing in blood. However, in the pump apparatus
disclosed in the patent document 1, it is impossible to find the position
of the impeller. Thus it is impossible to check whether the impeller is
rotating without contacting the inner surface of the housing with a
predetermined interval kept between the impeller and the inner surface of
the housing. The groove for hydrodynamic bearing of the pump apparatus
disclosed in the patent document 2 is used for an emergency such as the
failure of the sensor and not of the type of rotating the impeller by
always using the hydrodynamic pressure generated by the groove for
hydrodynamic bearing. The sensor does not measure the position of the
impeller when the impeller is rotated without contacting the housing by
the hydrodynamic pressure generated by the groove for hydrodynamic
bearing.

[0012]It is a second object of the present invention to provide a
centrifugal blood pump apparatus not of a type of magnetically levitating
an impeller but allowing a rotation of the impeller without substantial
contact between the impeller and a housing by utilizing a groove for
hydrodynamic bearing and allowing the position of the impeller to be
checked.

SUMMARY OF THE PRESENT INVENTION

[0013]The first object described above is attained by the following a
centrifugal fluid pump apparatus.

[0014]A centrifugal blood pump apparatus comprises a housing having a
blood inlet port and a blood outlet port; a centrifugal pump section
including an impeller having a magnetic material and rotating inside said
housing to feed a fluid by a centrifugal force generated during a
rotation thereof; an impeller rotational torque generation section for
attracting thereto said impeller of said centrifugal pump section and
rotating said impeller; and a portion, in which a groove for hydrodynamic
bearing is formed, provided on an inner surface of said housing at a side
of said impeller rotational torque generation section or a surface of
said impeller at said side of said impeller rotational torque generation
section, said impeller being rotated by said groove for hydrodynamic
bearing without contacting said housing, wherein a plurality of grooves
for hydrodynamic bearing is formed on said portion in which a groove for
hydrodynamic bearing is formed; each of said grooves for hydrodynamic
bearing has a first side and a second side both extending from a
periphery of said portion in which a groove for hydrodynamic bearing is
formed toward a central side thereof and opposed to each other, a third
side connecting one end of said first side and one end of said second
side to each other, and a fourth side connecting said other end of said
first side and said other end of said second side to each other; said
first side and said second side are formed as a circular arc respectively
in such a way that centers of said circular arcs are different from each
other; a value relating to a groove depth ratio a (a=h1/h2) computed from
a distance h1 between said impeller and said housing in said groove for
hydrodynamic bearing of said portion in which a groove for hydrodynamic
bearing is formed during a rotation of said impeller and from a distance
h2 between said impeller and said housing in a hydrodynamic bearing
groove-non-present portion of said portion in which a groove for
hydrodynamic bearing is formed during said rotation of said impeller is
in a range of 1.5 to 2.5; and a value relating to a groove width ratio s
(s=B0/B) computed from a width B0 of a peripheral portion of
each groove for hydrodynamic bearing and a sum B (B=B0+B1) of said
width B0 and a width B1 of a hydrodynamic bearing groove-non-present
portion between peripheral portions of adjacent grooves for hydrodynamic
bearing is in a range of 0.6 to 0.8.

[0015]Further, the first object described above is attained by the
following a centrifugal fluid pump apparatus.

[0016]A centrifugal blood pump apparatus comprises a housing having a
blood inlet port and a blood outlet port; a centrifugal pump section
including an impeller having a magnetic material and rotating inside said
housing to feed a fluid by a centrifugal force generated during a
rotation thereof; an impeller rotational torque generation section for
attracting thereto said impeller of said centrifugal pump section and
rotating said impeller; and a portion, in which a groove for hydrodynamic
bearing is formed, provided on an inner surface of said housing at a side
of said impeller rotational torque generation section or a surface of
said impeller at a side of said impeller rotational torque generation
section, said impeller being rotated by said groove for hydrodynamic
bearing without contacting said housing, wherein a plurality of grooves
for hydrodynamic bearing is formed on said portion in which a groove for
hydrodynamic bearing is formed; each of said grooves for hydrodynamic
bearing has a first side and a second side both extending from a
periphery of said portion in which a groove for hydrodynamic bearing is
formed toward a central side thereof and opposed to each other, a third
side connecting one end of said first side and one end of said second
side to each other, and a fourth side connecting said other end of said
first side and said other end of said second side to each other; said
first side and said second side are formed as a circular arc respectively
in such a way that centers of said circular arcs are different from each
other; and four corners composed of said four sides are rounded.

[0017]The second object described above is attained by the following a
centrifugal fluid pump apparatus.

[0018]A blood pump apparatus comprises a housing having a blood inlet port
and a blood outlet port; a pump section including an impeller having a
magnetic material disposed therein and rotating in said housing to feed
blood; and an impeller rotational torque generation section for
attracting thereto said impeller of said pump section and rotating said
impeller, wherein said pump section further comprises a groove for
hydrodynamic bearing provided on an inner surface of said housing at a
side of said impeller rotational torque generation section or a surface
of said impeller at said side of said impeller rotational torque
generation section, said impeller being rotated by said groove for
hydrodynamic bearing without contacting said housing, wherein said pump
section further comprises a sensor for measuring a position of said
impeller when said impeller is rotated without contacting said housing by
a hydrodynamic pressure generated by said groove for hydrodynamic
bearing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]The above and other objects, features and advantages of the present
invention will be better understood by reading the following description,
taken in conjunction with the accompanying drawings.

[0020]FIG. 1 is a front view showing a centrifugal blood pump apparatus
according to an embodiment of the present invention.

[0046]FIG. 1 is a front view showing a centrifugal blood pump apparatus
according to an embodiment of the present invention. FIG. 2 is a plan
view showing the centrifugal blood pump apparatus shown in FIG. 1. FIG. 3
is a vertical sectional view showing the centrifugal blood pump apparatus
of the embodiment shown in FIG. 1. FIG. 4 is a sectional view, taken
along a line A-A in FIG. 1, showing the centrifugal blood pump apparatus.
FIG. 5 is a sectional view showing a state in which an impeller is
removed from the sectional view, taken along a line A-A in FIG. 1,
showing the centrifugal blood pump apparatus.

[0047]A centrifugal blood pump apparatus 1 of the present invention
includes a housing 20 having a blood inlet port 22 and a blood outlet
port 23; a centrifugal pump section 2 including an impeller 21 having a
magnetic material 25 disposed therein and rotating inside the housing 20
to feed a fluid by a centrifugal force generated during its rotation; an
impeller rotational torque generation section 3 for attracting thereto
the magnetic material 25 of the impeller 21 of the centrifugal pump
section 2 and rotating the impeller 21; and a groove 38 for hydrodynamic
bearing (hereinafter referred to as hydrodynamic bearing groove) provided
on an inner surface of the housing 20 at the side of the impeller
rotational torque generation section 3 thereof or a surface of the
impeller 21 at the side of the impeller rotational torque generation
section 3 thereof. In the centrifugal blood pump apparatus 1, the
impeller 21 is rotated by the hydrodynamic bearing groove 38 without
contacting the housing 20.

[0048]In a first aspect of the centrifugal blood pump apparatus of the
present invention, each hydrodynamic bearing groove 38 has a first side
38a and a second side 38b both extending from the periphery of a portion
39 in which a groove for hydrodynamic bearing is formed toward the
central side thereof and opposed to each other, a third side 38c
connecting one end of the first side 38a and one end of the second side
38b to each other, and a fourth side 38d connecting the other end of the
first side 38a and the other end of the second side 38b to each other.
The first side 38a and the second side 38b are formed as a circular arc
respectively in such a way that the centers of the circular arcs are
different from each other. A value relating to a groove depth ratio a
(a=h1/h2) computed from a distance h1 between the impeller 21 and the
housing 20 in the hydrodynamic bearing groove of the portion in which a
hydrodynamic bearing groove is formed during a rotation of the impeller
21 and from a distance h2 between the impeller 21 and the housing 20 in
the hydrodynamic bearing groove-non-present portion (in other words, land
region) of the portion in which a hydrodynamic bearing groove is formed
during the rotation of the impeller 21 is in the range of 1.5 to 2.5. The
hydrodynamic bearing groove-non-present portion is said in other words as
land region. A value relating to a groove width ratio s (s=B0/B)
computed from a width B0 of a peripheral portion of each
hydrodynamic bearing groove and a sum B (B=B0+B1) of the width
B0 and a width B1 of a hydrodynamic bearing groove-non-present
portion between peripheral portions of adjacent grooves for hydrodynamic
bearing is in a range of 0.6 to 0.8.

[0049]Therefore the hydrodynamic bearing groove 38 is capable of obtaining
a load-carrying capacity almost equal to that of a logarithmic groove for
hydrodynamic bearing. In addition since the hydrodynamic bearing groove
38 is wider and shallower than the logarithmic groove for hydrodynamic
bearing having the same number of grooves, the hydrodynamic bearing
groove 38 generates a less amount of hemolysis.

[0050]In a second aspect of the centrifugal fluid pump apparatus of the
present invention, the hydrodynamic bearing groove 38 has the first side
38a and the second side 38b both extending from the periphery of the
portion 39 thereof in which a hydrodynamic bearing groove is formed
toward the central side thereof and opposed to each other, the third side
38c connecting one end of the first side 38a and one end of the second
side 38b to each other, and the fourth side 38d connecting the other end
of the first side 38a and the other end of the second side 38b to each
other. The first side 38a and the second side 38b are formed as the
circular arc respectively in such a way that the centers of the circular
arcs are different from each other. In addition, four corners 38e, 38f,
38g, and 38h composed of the four sides 38a, 38b, 38c, and 38d are
rounded.

[0051]The area of the hydrodynamic bearing groove whose corners are
rounded is smaller than the hydrodynamic bearing groove whose corners are
not rounded, although the load-carrying capacity of the corner-rounded
hydrodynamic bearing grooves decreases slightly. In addition, the
corner-rounded hydrodynamic bearing groove does not have a portion where
a pressure is excessively high. Thereby the corner-rounded hydrodynamic
bearing groove gives a smaller damage to blood than the hydrodynamic
bearing groove whose corners are not rounded and further causes blood to
stagnate to a lower extent than the hydrodynamic bearing groove whose
corners are not rounded. Therefore the corner-rounded hydrodynamic
bearing groove causes generation of hemolysis and thrombus to a lower
extent than the hydrodynamic bearing groove whose corners are not rounded
because the former causes blood to stagnate to a lower extent than the
latter.

[0052]The four corners of the hydrodynamic bearing groove are rounded at
not less than 0.1 mm. Thereby the hydrodynamic bearing groove causes the
hemolysis to occur to a lower extent.

[0053]It is preferable that the third side and the fourth side are formed
as a circular arc respectively in such a way that the circular arcs have
the same center and different radii. Thereby the hydrodynamic bearing
groove is readily machinable.

[0054]It is preferable that the centrifugal blood pump apparatus 1 of the
present invention has both the first and second aspects. The centrifugal
blood pump apparatus will be described below by using an embodiment
having both the first and second aspects.

[0055]In the centrifugal blood pump apparatus 1, the impeller is rotated
not with the impeller magnetically levitated but with the impeller out of
contact with the housing by means of the hydrodynamic bearing groove.
This construction eliminates the need for an electromagnet occupying a
larger area than other parts used for the magnetic levitation of the
impeller. Thus it is possible to make the centrifugal blood pump
apparatus compact.

[0056]As shown in FIGS. 1 through 5, the centrifugal blood pump apparatus
1 has the housing 20 having the blood inlet port 22 and the blood outlet
port 23; the centrifugal pump section 2 having the impeller 21 rotating
inside the housing 20 to feed blood by a centrifugal force generated
during its rotation; and the impeller rotational torque generation
section 3 for the impeller 21.

[0057]In the centrifugal blood pump apparatus 1 of this embodiment, the
impeller rotational torque generation section 3 has a rotor 31 having a
magnet 33 for attracting thereto the magnetic material 25 of the impeller
21; and a motor 34 for rotating the rotor 31.

[0058]As shown in FIG. 3, the impeller 21 rotates without contacting the
inner surface of the housing 20 by a pressure generated by the
hydrodynamic bearing groove 38 when the impeller 21 rotates.

[0059]The housing 20 has the blood inlet port 22 and the blood outlet port
23 and is formed of a non-magnetic material. The housing 20 accommodates
a blood chamber 24 communicating with the blood inlet port 22 and the
blood outlet port 23. The housing 20 also accommodates the impeller 21
therein. The blood inlet port 22 projects substantially vertically from
the vicinity of the center of the upper surface of the housing 20. The
blood inlet port 22 does not necessarily have to be formed as a straight
pipe, but may be formed as a curved pipe or a bent pipe. As shown in
FIGS. 2 and 4, the blood outlet port 23 projects tangentially from the
side surface of the approximately cylindrical housing 20.

[0060]As shown in FIG. 3, the disc-shaped impeller 21 having a
through-hole in the center thereof is accommodated inside the blood
chamber 24 formed inside the housing 20. As shown in FIGS. 3 and 4, the
impeller 21 includes an annular plate-shaped member (lower shroud) 27
forming the lower surface thereof, an annular plate-shaped member (upper
shroud) 28 forming the upper surface thereof and opening at the center
thereof, and a plurality of (for example, seven) vanes 18 formed between
the lower shroud 27 and the upper shroud 28. A plurality of (for example,
seven) blood passages 26 partitioned from one another by the adjacent
vanes 18 is formed between the lower shroud 27 and the upper shroud 28.
As shown in FIG. 4, each of the blood passages 26 communicates with the
center opening of the impeller 21 and extends from the center opening of
the impeller 21 to its periphery, with each of the blood passages 26
becoming gradually larger in the width thereof. In other words, the vanes
18 are formed between the adjacent blood passages 26. In the embodiment,
the vanes 18 and blood passages 26 are spaced at equiangular intervals
respectively and formed in substantially the same shape respectively.

[0061]As shown in FIGS. 3 and 4, a plurality (for example, 10 to 40) of
the magnetic materials 25 (for example permanent magnet, follower magnet)
are embedded in the impeller 21. In the embodiment, the magnetic
materials 25 are embedded in the lower shroud 27 of the impeller 21. A
permanent magnet 33, to be described later, provided in the rotor 31 of
the rotational torque generation section 3 attracts the magnetic material
25 embedded in the impeller 21 toward the side opposite to the side where
the blood inlet port 22 is disposed to allow the impeller 21 and the
rotor 31. In this operation, the magnetic material 25 serves as a means
for allowing to be magnetically coupled to each other and transmitting
the rotational torque from the rotational torque generation section 3 to
the impeller 21.

[0062]The magnetic coupling, to be described later, between the impeller
21 and the rotor 31 is ensured by embedding a plurality of the magnetic
materials 25 (permanent magnet) in the impeller 21. It is preferable that
each of the magnetic materials 25 is circular.

[0063]As shown in FIG. 3, the rotational torque generation section 3 has
the rotor 31 accommodated in the housing 20 and the motor 34 for rotating
the rotor 31. The rotor 31 has a plurality of permanent magnets 33
disposed on a surface thereof at the side of the centrifugal pump section
2. The center of the rotor 31 is fixedly secured to the rotational shaft
of the motor 34. A plurality of the permanent magnets 33 is equiangularly
distributed in accordance with the arrangement mode (number and position)
of the permanent magnets 25 of the impeller 21.

[0064]In the coupling between the permanent magnet of the impeller and
that of the motor, it is preferable to dispose the permanent magnet in
such a way that an attractive force is generated between the impeller and
the motor even though they are uncoupled from each other by an external
force and a power swing occurs therebetween. Thereby even though the
impeller and the motor are uncoupled from each other and the power swing
occurs therebetween, they can be coupled to each other easily again
because the attractive force is present therebetween.

[0065]As shown in FIG. 6, in the centrifugal blood pump apparatus 1 of the
embodiment, the housing 20 accommodates the impeller 21 and has the
groove 38 for hydrodynamic bearing formed on an inner surface 20a of the
housing 20, at the rotor-disposed side, forming the blood chamber 24. A
hydrodynamic bearing effect generated between the groove 38 for
hydrodynamic bearing and the impeller 21 by a rotation of the impeller 21
at a speed more than a predetermined number of rotations allows the
impeller 21 to rotate without contacting the inner surface of the housing
20.

[0066]As shown in FIG. 6, the groove 38 for hydrodynamic bearing has a
size corresponding to that of the bottom surface (surface at rotor side)
of the impeller 21. In the centrifugal blood pump apparatus 1 of the
embodiment, the groove 38 for hydrodynamic bearing extends spirally (in
other words, curved) outwardly to the vicinity of the outer edge of the
inner surface 20a, with one end of the groove 38 for hydrodynamic bearing
disposed on the periphery (circumference) of a circle spaced outward at a
short distance from the center of the inner surface 20a of the housing 20
and with the width thereof becoming outwardly gradually larger. A
plurality of the grooves 38 for hydrodynamic bearing has substantially
the same configuration and is spaced at almost equal intervals. Each of
the grooves 38 for hydrodynamic bearing is concavely formed. It is
preferable that the depth thereof is in the range of 0.05 to 0.4 mm. The
number of the groove 38 for hydrodynamic bearing is favorably in the
range of 6 to 36 and more favorably in the range of 8 to 24. In the
embodiment, 18 grooves 38 for hydrodynamic bearing are provided at
equiangular intervals around the axis of the impeller 21.

[0067]The groove 38 for hydrodynamic bearing may be disposed on the
rotor-side surface of the impeller 21 instead of disposing it at the
housing side. It is preferable that the groove 38 for hydrodynamic
bearing disposed on the rotor-side surface of the impeller 21 has the
same construction as that of the groove 38 for hydrodynamic bearing
disposed at the housing side.

[0068]The groove 38 for hydrodynamic bearing having the above-described
construction is attracted toward the impeller torque generation section
3. Owing to the hydrodynamic bearing effect generated between the groove
38 for hydrodynamic bearing disposed on the housing and the bottom
surface of the impeller 21 (or between the groove 38 for hydrodynamic
bearing disposed on the impeller and the inner surface of the housing),
the impeller 21 rotates without contacting the inner surface of the
housing 20 with the impeller 21 levitating slightly from the inner
surface of the housing 20, thus providing a blood passage between the
lower surface of the impeller 21 and the inner surface of the housing 20.
Thereby it is possible to prevent blood from staying therebetween and
thrombus from occurring because the blood is prevented from staying
therebetween.

[0069]In the pump apparatus 1, the hydrodynamic bearing groove 38 has the
first side 38a and the second side 38b both extending from the periphery
of the portion 39 thereof in which a hydrodynamic bearing groove is
formed toward the central side thereof and opposed to each other, the
third side 38c connecting one end of the first side 38a and one end of
the second side 38b to each other, and the fourth side 38d connecting the
other end of the first side 38a and the other end of the second side 38b
to each other. The first side 38a and the second side 38b are formed as a
circular arc respectively in such a way that the centers of the circular
arcs are different from each other. In this embodiment, the first side
38a and the second side 38b are composed of a circular arc respectively
in such a way that the circular arcs have different centers and radii.
Instead, the hydrodynamic bearing groove may be composed of circular arcs
having the same center and different radii or different centers and the
same radius. But the hydrodynamic bearing groove composed of circular
arcs having different centers and radii can be provided with a larger
width in the peripheral portion of the portion thereof in which a
hydrodynamic bearing groove is formed thereof than the hydrodynamic
bearing groove composed of circular arcs having the same center and
different radii or the hydrodynamic bearing groove composed of different
centers and the same radius.

[0070]In this embodiment, the third side 38c and the fourth side 38d are
formed as a circular arc respectively in such a way that the circular
arcs have the same center and different radii.

[0071]With reference to FIG. 6, the first side 38a is formed as the
circular arc having a radius Ra and a center disposed at a point P2
located outside the portion 39 in which a hydrodynamic bearing groove is
formed. The second side 38b is formed as the circular arc having a radius
Rb and a center disposed at a point P3 located outside the portion 39 in
which a hydrodynamic bearing groove is formed. Although the radius Ra
varies according to the size of the blood pump apparatus, the radius Ra
is set to preferably in the range of 30 to 70 mm. Although the radius Rb
varies according to the size of the blood pump apparatus, the radius Rb
is set to preferably in the range of 30 to 70 mm. It is preferable that
the distance between the points P2 and P3 is set to the range of 3 to 10
mm. The third side 38c is formed as the circular arc having a radius Rc
and a center disposed at a center P1 of the portion 39 in which a
hydrodynamic bearing groove is formed. The fourth side 38d is formed as
the circular arc having a radius Rd and a center disposed at the center
P1 of the portion 39 in which a hydrodynamic bearing groove is formed.
Although the radius Rc varies according to the size of the blood pump
apparatus, the radius Rc is set to preferably in the range of 6 to 18 mm.
Although the radius Rd varies according to the size of the blood pump
apparatus, the radius Rd is set to preferably in the range of 15 to 30
mm. It is preferable that the radius Rc is 0.3 to 0.8 times the radius
Rd.

[0072]As shown in FIG. 6, the value relating to a groove width ratio s
(s=B0/B) computed from the width B0 of the peripheral portion
of each hydrodynamic bearing groove and the sum B (B=B0+B1) of the
width B0 and the width B1 of the hydrodynamic bearing
groove-non-present portion between (land region) the peripheral portions
of the adjacent grooves for hydrodynamic bearing is in a range of 0.6 to
0.8.

[0073]As shown in FIG. 7, in the pump apparatus of this embodiment, the
hydrodynamic bearing groove 38 composed of the four sides 38a, 38b, 38c,
and 38d, four corners 38e, 38f, 38g, and 38h are rounded. The four
corners of said groove for hydrodynamic bearing are rounded at not less
than 0.1 mm.

[0074]With reference to FIG. 8, the value relating to a groove depth ratio
a (a=h1/h2) computed from the distance h1 between the impeller 21 and the
housing 20 in the hydrodynamic bearing groove of the portion in which a
hydrodynamic bearing groove is formed during the rotation of the impeller
21 and from the distance h2 between the impeller 21 and the housing 20 in
the hydrodynamic bearing groove-non-present portion of the portion in
which a hydrodynamic bearing groove is formed during the rotation of the
impeller 21 is in the range of 1.5 to 2.5.

[0075]As described above, since the hydrodynamic bearing groove 38 is so
constructed that the value relating to a groove width ratio s
(s=B0/B) is in the range of 0.6 to 0.8 and that the value relating
to a groove depth ratio a (a=h1/h2) is in the range of 1.5 to 2.5, the
hydrodynamic bearing groove 38 is wider and shallower than a logarithmic
groove for hydrodynamic bearing having the same number of grooves. Thus
the hydrodynamic bearing groove 38 generates a less amount of hemolysis.

[0076]In the case of a groove having the configuration of a logarithmic
spiral groove shown in FIG. 14, the load-carrying capacity can be
computed, supposing that the outer radius of the groove is r2, the inner
radius thereof is rb, the fluid inlet angle of the groove is α, the
ratio of the width of the groove to that of the land is a1/a2, the number
of grooves is N, the depth of the groove is h1, the number of rotations
is w, and the viscosity is μ. For the hydrodynamic bearing groove
having configurations other than the configuration shown in FIG. 14,
appropriate parameters are determined by analyzing the flow of a fluid
three-dimensionally and finding the load-carrying capacity or using
results obtained by theoretically analyzing the flow of the fluid
two-dimensionally (only sectional configuration of groove is considered
and longitudinal dimension thereof orthogonal to the section thereof is
considered to be sufficiently longer than sectional dimension). In this
embodiment, the latter designing method is adopted.

[0089]The change of Wd-less for a and s is as shown in FIG. 9. FIG. 9
indicates that there is (efficient) s (Bo/B) which provides a
maximum load-carrying capacity for desired h1 and h2. Therefore
it is possible to obtain a sufficient load-carrying capacity by
appropriately setting h1, h2, B, Bo, and L which are
parameters of the configuration of the hydrodynamic bearing groove.

[0090]FIG. 9 indicates that a=1.5 to 2.5 and s=0.6 to 0.8 fall in a
practical range (value not less than 0.8 times maximum value).

[0091]In the case of the centrifugal pump, the outer and inner diameters
of the impeller are designated. Thereby the outer and inner diameters of
the groove are designated. Supposing that the diameter of the impeller is
50 mm, the outer diameter D2 of the groove D2=50 mm, and the inner
diameter Db of the groove>20 mm, as the value relating to a groove
depth ratio a and the value relating to a groove width ratio s, a=1.8 and
s=0.65 are selected respectively to design the groove. The selection was
made by setting the interval between adjacent grooves to not less than
0.5 mm.

[0092]When a=1.866 and s=0.7182, the load-carrying capacity is maximum.
The values of Wd-less are 0.203 and 0.206 different by 1.5%, namely,
almost equal. The impeller is desired to levitate by 0.1 mm (h2 in FIG.
8) by setting the value relating to a groove depth to 1.8. Thus the depth
of the groove is 0.08 mm. In this case, a=1+0.08/0.1=1.8.

[0093]The procedure of designing the groove at the current time is shown
below. FIG. 5 shows the final configuration of the groove.

[0094](1) The outer diameter of the impeller is set to φ50. Thus the
outer diameter of the groove is set to φ50.

[0095](2) The inner diameter of the impeller is set to φ20. Thus the
outer diameter of the groove can be set to not less than φ20.

[0096]The solution of (r2-rb)/(r2-r1) is aimed to be 0.7 to 0.8. Thus the
inner radius of the groove rb is set to 14. In this case, the solution of
(r2-rb)/(r2-r1)=0.73. Thereby two sides of the groove is determined.

[0097](3) Thereafter a circle having a radius of 58 (unit: mm) is drawn
with the center thereof disposed at a point (36, -31), when the center of
the inner and diameters of the hydrodynamic bearing groove is disposed at
the origin. The point (36, -31) and the radius 58 are designated from a
desired fluid inlet angle (15 to 60 degrees) of the groove. Thereby three
sides of the groove are determined. The midpoint between the radius 14 mm
and the radius 25 mm is on the circumference of a circle having a
diameter 19.5 mm. The angle formed between the x-axis and the point of
intersection of the two circles is 72.36 degrees. Thus the coordinate of
the point of intersection is (5.91, 18.58).

[0098](4) Thereafter the width of the groove is determined so that s=0.65
on the circumference of a circle having a radius 19.5. At the current
time, the number of grooves is set to 18. Thus the grooves are formed at
intervals of 20 degrees. When the diameter of the impeller (diameter of
portion in which a hydrodynamic bearing groove is formed) is about 50 mm,
it is appropriate that the number of the grooves is 15 to 20. When
s=0.65, the angle of the groove is 20×0.65=13 degrees. Thus, from
72.36-13=59.36 degrees, the coordinate of the midpoint on the
circumference opposed to the groove is (9.94, 16.78):

19.5 cos(59.36°)=9.94

19.5 sin(59.36°)=16.78

[0099]A circle whose radius is equal to the distance between this point
and the point (35, -37) is drawn, with the center thereof disposed at a
point (35, -37). Thereby the four sides of the groove are determined.

[0100]The point (35, -37) is designated in advance from the desired fluid
inlet angle (15 to 60 degrees) of the groove.

[0101](5) The four corners of the groove are rounded at R0.5. The four
corners may be rounded at R1. When the four corners are rounded at a very
generous radii, the load-carrying capacity becomes small. Supposing that
a milling machine is used to machine the groove, it is proper that the
four corners of the groove are rounded at R0.5 in view of the diameter of
an end mill.

[0102](6) The grooves of 17 are drawn. FIG. 15 shows hydrodynamic bearing
grooves designed in the same condition and same size as the above. The
number of the grooves is slightly different from the above condition. By
using the results of the designed hydrodynamic bearing grooves,
measurement was conducted on a levitation amount (distance between
impeller and land on surface of rotor) of the case in which the
hydrodynamic bearing groove of the present invention was mounted on the
pump (diameter of impeller: 40, 50 mm) having the construction shown in
FIG. 3 and the case in which a conventional logarithmic spiral groove was
mounted on the pump having the construction shown in FIG. 3 (in both
cases, magnetic coupling force between impeller and rotor was set
equally). As a result, the levitation amounts were equal to each other.
This means that the load-carrying capacity generated by the hydrodynamic
bearing groove of the present invention is equal to that generated by the
conventional logarithmic spiral groove. Although the load-carrying
capacities are equal to each other, the configuration of the hydrodynamic
bearing groove of the present invention shown in FIG. 5 has the following
advantages over the configuration of the conventional logarithmic spiral
groove shown in FIG. 5.

[0103](a) The configuration of the groove of the present invention allows
its depth to be smaller and its width to be larger than that of the
configuration of the conventional logarithmic spiral groove. This means
that the configuration of the former gives a smaller damage to a red
blood cell than that of the latter and advantageous over the latter in
terms of hemolysis.

[0104](b) As described above, the configuration of the former allows the
depth of the groove to be smaller than that of the latter. This is
advantageous in designing the hydrodynamic bearing groove. That is, in
the case of the blood pump having the construction shown in FIG. 3, it is
necessary to shorten the distance between the impeller and the rotor to
some extent to secure the rigidity of the groove. This is because the
force of the magnetic coupling between the impeller and the rotor is low
when the distance therebetween is long. Consequently the rigidity
deteriorates when the impeller levitates. Therefore there is a
restriction on the thickness of the surface of the housing on which the
hydrodynamic bearing groove is formed. It is necessary that the surface
on which the hydrodynamic bearing groove is formed is strong because the
motor is mounted thereon. As such it is possible to secure a desired
strength for the surface on which the hydrodynamic bearing groove is
formed by making the depth of the groove shallow. Further the shallow
groove can be designed more easily than the deeper groove. In the
construction shown in FIG. 3, the hydrodynamic bearing groove is formed
only on the rotor-side surface of the housing. But it is conceivable to
form the hydrodynamic bearing groove on the surface of the housing at the
side of the blood inlet port to apply a hydrodynamic pressure to both
surfaces of the impeller. In this case, there is no fear that the
impeller and the rotor are magnetically uncoupled from each other owing
to a large amount of movement of the impeller toward the blood inlet port
caused by a great hydrodynamic pressure generated at the rotor side. As
such it is possible to increase the levitation amount of the impeller
when the impeller rotates at a low number of rotations by proving a
magnetic coupling on the surface of the housing at the side of the blood
inlet port. When the magnetic coupling is provided on the surface of the
housing at the side of the blood inlet port, there is a restriction to
the thickness of the surface of the housing at the side of the blood
inlet port similarly to the restriction placed on the thickness of the on
the rotor-side surface of the housing. In this respect, to make the
hydrodynamic bearing groove shallow is advantageous in designing the
hydrodynamic bearing groove.

[0105]A centrifugal blood pump apparatus according to another embodiment
of the present invention is described below.

[0106]FIG. 10 is a front view showing a centrifugal blood pump apparatus
according to another embodiment of the present invention. FIG. 11 is a
vertical sectional view showing the centrifugal blood pump apparatus of
the embodiment shown in FIG. 10. FIG. 12 is a sectional view, taken along
a line B-B in FIG. 10, showing the centrifugal blood pump apparatus. FIG.
13 is a bottom view showing the centrifugal blood pump apparatus shown in
FIG. 10. A plan view of the centrifugal blood pump apparatus according to
the embodiment shown in FIG. 10 is the same as the plan view shown in
FIG. 2. A sectional view showing the impeller removed from a sectional
view taken along a line B-B in FIG. 10 is the same as the sectional view
shown in FIG. 5. Therefore they are omitted herein.

[0107]A pump apparatus 50 of this embodiment is different from the pump
apparatus 1 of the above-described embodiment in only the mechanism of
the impeller rotational torque generation section 3. The impeller
rotational torque generation section 3 of the pump apparatus 50 does not
have a rotor, but is of a type of driving the impeller directly. In the
pump apparatus 50 of this embodiment, the impeller 21 rotates without
contacting the inner surface of the housing 20 by a pressure generated by
the hydrodynamic bearing groove 38 when the impeller 21 rotates. In
description that is described below, constructions different from those
of the above-described embodiment are described. The mode of the
hydrodynamic bearing groove 38 is the same as that of the above-described
embodiment.

[0108]As shown in FIGS. 11, 12 and 13, the impeller rotational torque
generation section 3 of the pump apparatus 50 has a plurality of stator
coils 61 accommodated in the housing 20. The stator coils 61 are disposed
along a circumference at equiangular intervals around the axis thereof.
More specifically, six stator coils 61 are used. Multilayer stator coils
are used as the stator coils 61. A rotating magnetic field is generated
by switching the direction of electric current flowing through each
stator coil 61. The impeller is attracted by the rotating magnetic field
and rotates.

[0109]As shown in FIG. 12, a plurality (for example, 6 to 12) of the
magnetic materials 25 (for example, permanent magnet, follower magnet) is
embedded in the impeller 21. In the embodiment, the magnetic materials 25
are embedded in the lower shroud 27. The stator coils 61 provided in the
rotational torque generation section 3 attracts the magnetic material 25
embedded in the impeller toward the side opposite to the side where the
blood inlet port 22 is disposed. In this operation, the magnetic
materials 25 couple to the operation of the stator coils 61 and transmit
the rotational torque from the rotational torque generation section 3 to
the impeller 21.

[0110]The magnetic coupling, to be described later, between the impeller
21 and the stator rotor 61 is ensured by embedding a plurality of the
magnetic materials 25 (permanent magnet) in the impeller 21. It is
preferable that each of the magnetic materials 25 is approximately
trapezoidal. The magnetic materials 25 are ring-shaped or plate-shaped.
It is preferable that the number and arrangement mode of the magnetic
materials 25 correspond to those of the stator coils 61. The magnetic
materials 25 are disposed circumferentially at equiangular intervals
around the axis of the impeller in such a way that positive and negative
poles thereof alternate with each other.

[0111]FIG. 16 is a block diagram of an embodiment including a control
mechanism of a blood pump apparatus of the present invention. FIG. 17 is
a front view showing a blood pump apparatus according to still another
embodiment of the present invention. FIG. 18 is a plan view showing the
blood pump apparatus shown in FIG. 17. FIG. 19 is a sectional view taken
along a line C-C in FIG. 18. FIG. 20 is a sectional view taken along a
line D-D in FIG. 19. FIG. 21 is a sectional view showing a state in which
an impeller is removed from the sectional view taken along a line D-D in
FIG. 19. FIG. 22 is a sectional view showing a state in which an impeller
is removed from the sectional view taken along a line E-E in FIG. 19.

[0112]A blood pump apparatus 100 of the present invention includes a
housing 20 having a blood inlet port 22 and a blood outlet port 23; a
pump section 2 including an impeller 21 having a magnetic material 25
disposed therein and rotating in the housing 20 to feed blood; and an
impeller rotational torque generation section 3 for attracting thereto
the impeller 21 of the pump section 2 and rotating the impeller 21. The
pump section 2 further includes a first groove 38 for hydrodynamic
bearing provided on an inner surface of the housing 20 at the side of the
impeller rotational torque generation section 3 or a surface of the
impeller 21 at the side of the impeller rotational torque generation
section 3. The impeller 21 rotates without contacting the housing 20. The
pump section 2 has a sensor 45 having a function of measuring the
position of the impeller 21 when the impeller 21 is rotated without
contacting the housing 20 by a hydrodynamic pressure generated by the
hydrodynamic bearing groove 38.

[0113]Therefore in the blood pump apparatus of this embodiment, the
impeller is rotated without contacting the housing 20 by utilizing the
hydrodynamic bearing groove, and the position of the impeller can be
checked.

[0114]As shown in FIGS. 17 through 22, the blood pump apparatus 100 of
this embodiment is a centrifugal blood pump apparatus and has the housing
20 having the blood inlet port 22 and the blood outlet port 23, the
centrifugal pump section 2 having the impeller 21 rotating inside the
housing 20 to feed blood by a centrifugal force generated during its
rotation, and the impeller rotational torque generation section 3 for the
impeller 21.

[0115]The blood pump apparatus of the embodiment of the present invention
is not limited to the above-described centrifugal pump apparatus. For
example, the blood pump apparatus may be of an axial-flow type or of a
diagonal-flow type.

[0116]In the centrifugal blood pump apparatus 100 of this embodiment, the
impeller rotational torque generation section 3 has a rotor 31 having a
magnet 33 for attracting thereto a magnetic material 25 of the impeller
21 and a motor 34 for rotating the rotor 31.

[0117]As shown in FIG. 19, the impeller 21 rotates without contacting the
inner surface of the housing 20 by a pressure generated by the
hydrodynamic bearing groove when the impeller 21 rotates.

[0118]The housing 20 has the blood inlet port 22 and the blood outlet port
23 and is formed of a non-magnetic material. The housing 20 accommodates
a blood chamber 24 communicating with the blood inlet and outlet ports 22
and 23. The housing 20 also accommodates the impeller 21 therein. The
blood inlet port 22 projects substantially vertically from the vicinity
of the center of the upper surface of the housing 20. The blood inlet
port 22 does not necessarily have to be formed as a straight pipe, but
may be formed as a curved pipe or a bent pipe. As shown in FIGS. 18, 20,
21, and 22, the blood outlet port 23 projects tangentially from a side
surface of the approximately cylindrical housing 20.

[0119]As shown in FIG. 19, the disc-shaped impeller 21 having a
through-hole in the center thereof is accommodated inside the blood
chamber 24 formed inside the housing 20. As shown in FIGS. 18 and 19, the
impeller 21 includes an annular plate-shaped member (lower shroud) 27
forming the lower surface thereof, an annular plate-shaped member (upper
shroud) 28 forming the upper surface thereof and opening at the center
thereof, and a plurality of (for example, seven) vanes 18 formed between
the lower shroud 27 and the upper shroud 28. A plurality (for example,
seven) of blood passages 26 partitioned from one another by the adjacent
vanes 18 is formed between the lower shroud 27 and the upper shroud 28.
As shown in FIG. 19, each of the blood passages 26 communicates with the
center opening of the impeller 21 and extends from the center opening of
the impeller 21 to its periphery, with each of the blood passages 26
becoming gradually larger in the width thereof. In other words, each vane
18 is formed between the adjacent blood passages 26. In the embodiment,
the vanes 18 and blood passages 26 are spaced at equiangular intervals
respectively and formed in substantially the same shape respectively.

[0120]As shown in FIGS. 19 and 20, a plurality (for example, 10 to 40) of
the magnetic materials 25 (for example permanent magnet, follower magnet)
are embedded in the impeller 21. In the embodiment, the magnetic
materials 25 are embedded in the lower shroud 27. A permanent magnet 33,
to be described later, provided in the rotor 31 of the rotational torque
generation section 3 attracts the magnetic material 25 embedded in the
impeller toward the side opposite to the side where the blood inlet port
22 is disposed. In this operation, the magnetic material 25 serves as a
means for allowing the impeller 21 and the rotor 31 to be magnetically
coupled to each other and transmitting the rotational torque from the
rotational torque generation section 3 to the impeller 21.

[0121]The magnetic coupling, to be described later, between the impeller
21 and the rotor 31 is ensured by embedding a plurality of the magnetic
materials 25 (permanent magnet) in the impeller 21. It is preferable that
each of the magnetic materials 25 is circular.

[0122]As shown in FIG. 19, included in the rotational torque generation
section 3 are the rotor 31 accommodated in the housing 20 and a motor 34
for rotating the rotor 31. The rotor 31 has a plurality of permanent
magnets 33 disposed on a surface thereof at the side of the centrifugal
pump section 2. The center of the rotor 31 is fixedly secured to the
rotational shaft of the motor 34. A plurality of the permanent magnets 33
is equiangularly distributed in accordance with the arrangement mode
(number and position) of the permanent magnets 25 of the impeller 21.

[0123]In the coupling between the permanent magnet of the impeller and
that of the motor, it is preferable to dispose the permanent magnet in
such a way that an attractive force is generated between the impeller and
the motor even though they are uncoupled from each other by an external
force and a power swing occurs therebetween. Thereby even though the
impeller and the motor are uncoupled from each other and the power swing
occurs therebetween, they can be coupled to each other easily again
because the attractive force is present therebetween.

[0124]As shown in FIGS. 18 and 19, in this embodiment, the impeller 21 has
a plurality of a ring-shaped permanent magnet 29. In the embodiment, the
permanent magnet 29 is embedded in the upper shroud 28. A second
permanent magnet 41 attracts the permanent magnet 29 embedded in the
impeller toward the side opposite to the side where the impeller
rotational torque generation section 3 (namely, rotor) is disposed. The
permanent magnet 29 is so disposed that an attractive force is generated
between the permanent magnet 29 and the second permanent magnet 41. The
permanent magnet 29 may be plural (for example, 10 to 40) provided.

[0125]As shown in FIG. 21, in the centrifugal blood pump apparatus 100 of
the embodiment, the housing 20 accommodates the impeller 21 and has the
first groove 38 for hydrodynamic bearing formed on a rotor-side inner
surface 20a of the housing 20 forming the blood chamber 24. A
hydrodynamic bearing effect generated between the first groove 38 for
hydrodynamic bearing and the impeller 21 by a rotation of the impeller 21
at a speed more than a predetermined number of rotations allows the
impeller 21 to rotate without contacting the inner surface of the housing
20.

[0126]As shown in FIGS. 18 and 19, the centrifugal pump section 2 has at
least one fixed permanent magnet 41 for attracting thereto the magnetic
material 29 (embedded in upper shroud 28) of the impeller 21 provided
separately from the magnetic material 25 of the impeller 21. More
specifically, as shown with broken lines in FIG. 18, the circular
arc-shaped permanent magnet 41 is plural used. The impeller 21 is
attracted to opposite directions by the permanent magnet 33 of the rotor
31 and the permanent magnet 41. The permanent magnets 41 are provided at
equiangular intervals around the axis of the impeller 21. It is possible
to use not less than three permanent magnets 41, for example, four
permanent magnets 41.

[0127]The blood pump section 2 has a sensor 45 having a function of
measuring the position of the impeller 21. More specifically, the blood
pump section 2 has a plurality of position sensors 45 accommodated in the
housing 20. The position sensors (three) 45 are spaced at equiangular
intervals around the axis of the impeller 21. The electromagnets 41 are
also spaced at equiangular intervals around the axis of the impeller 21.
By providing the three position sensors 45, it is possible to measure the
inclination of the impeller 21 in the direction of the rotational axis
(z-axis) and in the direction of an x-axis and a y-axis orthogonal to the
rotational axis (z-axis). The position sensors 45 detect the gap between
them and the magnetic material 29. As shown in FIG. 16, outputs of the
position sensors 45 are transmitted to a control part 51 of the control
unit 6 controlling motor current.

[0128]The control unit 6 has a sensor unit 57 for the sensors 45, the
control part 51, a power amplifier 52 for the motor, a motor control
circuit 53, and a motor current monitoring part 55.

[0129]It is preferable that the blood pump apparatus has a blood
viscosity-computing function of computing a blood viscosity by using the
output of the position sensor 45. More specifically, the control unit 6
has a viscosity-measuring function. The blood viscosity-computing
function includes a function of temporarily decreasing the number of
rotations of the impeller to a predetermined number of rotations; and a
function of detecting a vertical swivel length of the impeller by using
the output of the sensor when the number of rotations of the impeller has
decreased to the predetermined number of rotations by the function of
temporarily decreasing the number of rotations and computing the blood
viscosity by using the detected vertical swivel length. It is preferable
that the blood viscosity-computing function has a storing part for
storing data of the relationship between the vertical swivel length of
the impeller and the blood viscosity at the predetermined number of
rotations of the impeller or a viscosity-computing equation obtained from
the data of the relationship and a viscosity-computing function for
computing the blood viscosity from data of the vertical swivel length
obtained by the output of the sensor and the data of the relationship
between the vertical swivel length of the impeller and the blood
viscosity stored by the storing part or the viscosity-computing equation.

[0130]More specifically, in the blood pump apparatus 100 of this
embodiment, the control unit 6 has the function of temporarily decreasing
the number of rotations of the motor to a predetermined number of
rotations by adjusting motor current, stores relation data for various
blood viscosities between vertical swivel movements (indicated by μm
peak to peak in vertical swivel movement of the impeller) of the impeller
at predetermined number of rotations of the motor and blood viscosity,
and has the function of computing the blood viscosity from results
detected by the sensor and the number of rotations of the motor.

[0131]With reference to FIG. 18, when the distance between the position
sensor and the impeller is detected by the position sensor 45 spaced at
120 degrees, the output of the position sensor 45 fluctuates like a sine
wave in a period (for example, 0.05 seconds at 1200 rpm) of the number of
rotations of the motor. The peak to peak of the sine wave indicates the
vertical swivel of the impeller. The vertical swivel is as shown in table
1 when the centrifugal hydrodynamic bearing pump has the impeller having
a diameter of 40 mm.

[0132]The state of the blood outlet port is shown in conditions of "Open"
and "Close" normally used for a pump. The higher the viscosity, the
smaller the vertical swivel when the impeller rotates at a small number
of rotations (1000 rpm) at which the hydrodynamic pressure effect is not
displayed at the blood inlet port. On the other hand, at 1500 rpm, the
vertical swivel length is reduced by the display of the hydrodynamic
pressure effect at the blood inlet port. This relationship is measured in
advance for a plurality of viscosities (for example, intervals of 1 mPas
at 2 to 5 mPas) at predetermined number of rotations (for example, 800 to
1200 rpm) of the impeller, and in addition, data of results of the
measurement or relational expression data obtained from the data of
results of the measurement is stored. Thereafter the viscosity of the
blood is computed from a measured value of the vertical swivel and the
above-described data. The vertical swivel varies to some extent in
dependence on the state of the blood outlet port. When the blood pump
apparatus is used as an auxiliary artificial heart of an organism, a
state close to "Open" or "Close" can be found from a change in the motor
current. The vertical swivel at that time is selected.

[0133]The pump apparatus 100 of the present invention has the first groove
38 for hydrodynamic bearing provided on an inner surface of the housing
20 at the side of the impeller rotational torque generation section 3
thereof or a surface of the impeller 21 at the side of the impeller
rotational torque generation section 3 thereof.

[0134]As shown in FIG. 21, the first groove 38 for hydrodynamic bearing
has a size corresponding to that of the bottom surface (surface at rotor
side) of the impeller 21. As shown in FIG. 6, the first groove 38 for
hydrodynamic bearing extends spirally (in other words, curved) outwardly
to the vicinity of the outer edge of the inner surface 20a, with one end
of the first groove 38 for hydrodynamic bearing disposed on the periphery
(circumference) of a circle spaced outward at a short distance from the
center of the inner surface 20a of the housing 20 and with the width
thereof becoming outwardly gradually larger. The first groove 38 for
hydrodynamic bearing is composed of a group of a large number of grooves
for hydrodynamic bearing. The first grooves 38 have substantially the
same configuration and are spaced at almost equal intervals. Each of the
first grooves 38 for hydrodynamic bearing is concavely formed. It is
preferable that the depth thereof is in the range of 0.05 to 0.4 mm. The
number of the first grooves 38 for hydrodynamic bearing is favorably in
the range of 6 to 36. In the embodiment, 16 grooves for hydrodynamic
bearing are provided at equiangular intervals around the axis of the
impeller 21.

[0135]The groove for hydrodynamic bearing may be disposed on the
rotor-side surface of the impeller 21 instead of disposing it at the
housing side. It is preferable that the groove for hydrodynamic bearing
disposed on the rotor-side surface of the impeller 21 has the same
construction as that of the groove for hydrodynamic bearing disposed at
the housing side.

[0136]The first groove 38 for hydrodynamic bearing is attracted toward the
impeller torque generation section 3. Owing to the hydrodynamic bearing
effect generated between the first groove 38 for hydrodynamic bearing
disposed on the housing and the bottom surface of the impeller 21 (or
between the first groove 38 for hydrodynamic bearing disposed on the
impeller and the inner surface of the housing), the impeller 21 rotates
without contacting the inner surface of the housing 20 with the impeller
21 levitating slightly from the inner surface of the housing 20, thus
providing a blood passage between the lower surface of the impeller 21
and the inner surface of the housing 20. Thereby it is possible to
prevent blood from staying therebetween and thrombus from occurring
because the blood is prevented from staying therebetween.

[0137]In pump apparatus of the present invention, as shown in FIGS. 20 and
6, each hydrodynamic bearing groove 38 has a first side 38a and a second
side 38b both extending from the periphery of the portion 39 thereof in
which a hydrodynamic bearing groove is formed toward the central side
thereof and opposed to each other, a third side 38c connecting one end of
the first side 38a and one end of the second side 38b to each other, and
a fourth side 38d connecting the other end of the first side 38a and the
other end of the second side 38b to each other. The first side 38a and
the second side 38b are formed as a circular arc respectively in such a
way that the centers of the circular arcs are different from each other.

[0138]In this embodiment, the first side 38a and the second side 38b are
composed of a circular arc respectively in such a way that the circular
arcs have different centers and radii. Instead, the hydrodynamic bearing
groove may be composed of circular arcs having the same center and
different radii or different centers and the same radius. But the
hydrodynamic bearing groove composed of circular arcs having different
centers and radii can be provided with a larger width in the peripheral
portion of the portion in which a hydrodynamic bearing groove is formed
thereof than the hydrodynamic bearing groove composed of circular arcs
having the same center and different radii or the hydrodynamic bearing
groove composed of different centers and the same radius.

[0139]In this embodiment, the third side 38c and the fourth side 38d are
formed as a circular arc respectively in such a way that the circular
arcs have the same center and different radii.

[0140]With reference to FIG. 6, the first side 38a is formed as the
circular arc having a radius Ra and a center disposed at a point P2
located outside the portion 39 in which a hydrodynamic bearing groove is
formed. The second side 38b is formed as the circular arc having a radius
Rb and a center disposed at a point P3 located outside the portion 39 in
which a hydrodynamic bearing groove is formed. Although the radius Ra
varies according to the size of the blood pump apparatus, the radius Ra
is set to preferably in the range of 30 to 70 mm. Although the radius Rb
varies according to the size of the blood pump apparatus, the radius Rb
is set to preferably in the range of 30 to 70 mm. It is preferable that
the distance between the points P2 and P3 is set to the range of 3 to 10
mm. The third side 38c is formed as the circular arc having a radius Rc
and a center disposed at a center P1 of the portion 39 in which a
hydrodynamic bearing groove is formed. The fourth side 38d is formed as
the circular arc having a radius Rd and a center disposed at the center
P1 of the portion 39 in which a hydrodynamic bearing groove is formed.
Although the radius Rc varies according to the size of the blood pump
apparatus, the radius Rc is set to preferably in the range of 6 to 18 mm.
Although the radius Rd varies according to the size of the blood pump
apparatus, the radius Rd is set to preferably in the range of 15 to 30
mm. It is preferable that the radius Rc is 0.3 to 0.8 times the radius
Rd.

[0141]As shown in FIG. 6, the value relating to a groove width ratio s
(s=B0/B) computed from the width B0 of the peripheral portion
of each hydrodynamic bearing groove and the sum B (B=B0-B1) of the
width B0 and the width B1 of the hydrodynamic bearing
groove-non-present portion between the peripheral portions of the
adjacent grooves for hydrodynamic bearing is in a range of 0.6 to 0.8.

[0142]As shown in FIG. 7, in the pump apparatus of this embodiment, the
hydrodynamic bearing groove 38 composed of the four sides 38a, 38b, 38c,
and 38d, four corners 38e, 38f, 38g, and 38h are rounded. It is
preferable that the four corners are rounded at not less than 0.1 mm.

[0143]With reference to FIG. 8, the value relating to a groove depth ratio
a (a=h1/h2) computed from the distance h1 between the impeller 21 and the
housing 20 in the hydrodynamic bearing groove of the portion in which a
hydrodynamic bearing groove is formed during the rotation of the impeller
21 and from the distance h2 between the impeller 21 and the housing 20 in
the hydrodynamic bearing groove-non-present portion of the portion in
which a hydrodynamic bearing groove is formed during the rotation of the
impeller 21 is in the range of 1.5 to 2.5.

[0144]As described above, since the hydrodynamic bearing groove 38 is so
constructed that the value relating to a groove width ratio s
(s=B0/B) is in the range of 0.6 to 0.8 and that the value relating
to a groove depth ratio a (a=h1/h2) is in the range of 1.5 to 2.5, the
hydrodynamic bearing groove 38 is wider and shallower than a logarithmic
groove for hydrodynamic bearing having the same number of grooves. Thus
the hydrodynamic bearing groove 38 generates a less amount of hemolysis.

[0145]As shown in FIG. 22, a second groove 71 for hydrodynamic bearing has
a size corresponding to that of the upper surface (surface at permanent
magnet side) of the impeller 21. As shown in FIG. 6, the second groove 71
for hydrodynamic bearing extends spirally (in other words, curved)
outwardly to the vicinity of the outer edge of the inner surface 20a,
with one end of the second groove 71 for hydrodynamic bearing disposed on
the periphery (circumference) of a circle spaced outward at a short
distance from the center of the inner surface 20a of the housing 20 and
with the width thereof becoming outwardly gradually larger. A plurality
of the grooves 71 for hydrodynamic bearing has substantially the same
configuration and is spaced at almost equal intervals. Each of the second
groove 71 for hydrodynamic bearing is concavely formed. It is preferable
that the depth thereof is in the range of 0.05 to 0.4 mm. The number of
the second groove 71 for hydrodynamic bearing is favorably in the range
of 6 to 36. In the embodiment, 16 grooves for hydrodynamic bearing are
provided at equiangular intervals around the axis of the impeller 21.

[0146]The groove for hydrodynamic bearing may be disposed on the permanent
magnet-side surface of the impeller 21 instead of disposing it at the
housing side. It is preferable that the groove for hydrodynamic bearing
disposed on the permanent magnet-side surface of the impeller 21 has the
same construction as that of the groove for hydrodynamic bearing disposed
at the housing side.

[0147]The blood pump apparatus 100 has the second hydrodynamic bearing
groove 71. Thereby even though the impeller is proximate to a portion of
the housing at the side of the second hydrodynamic bearing groove 71 when
an excessive hydrodynamic pressure is generated by a disturbance or by
the first hydrodynamic bearing groove, it is possible to prevent the
impeller from contacting the portion of the housing at the side of the
second hydrodynamic bearing groove 71 because a hydrodynamic pressure is
generated by the second hydrodynamic bearing groove.

[0148]In the embodiment, as shown in FIGS. 21, 6, and 7, similarly to the
hydrodynamic bearing groove 38, each hydrodynamic bearing groove 71 has a
first side 38a and a second side 38b both extending from the periphery of
the portion 39 thereof in which a hydrodynamic bearing groove is formed
toward the central side thereof and opposed to each other, a third side
38c connecting one end of the first side 38a and one end of the second
side 38b to each other, and a fourth side 38d connecting the other end of
the first side 38a and the other end of the second side 38b to each
other. The first side 38a and the second side 38b are formed as a
circular arc respectively in such a way that the centers of the circular
arcs are different from each other. In this embodiment, the first side
38a and the second side 38b are composed of a circular arc respectively
in such a way that the circular arcs have different centers and radii. In
this embodiment, the third side 38c and the fourth side 38d are formed as
a circular arc respectively in such a way that the circular arcs have the
same center and different radii.

[0149]In the pump apparatus of the present invention, as shown in FIG. 8,
the value relating to a groove depth ratio a (a=h1/h2) computed from the
distance h1 between the impeller 21 and the housing 20 in the
hydrodynamic bearing groove of the portion in which a hydrodynamic
bearing groove is formed during the rotation of the impeller 21 and from
the distance h2 between the impeller 21 and the housing 20 in the
hydrodynamic bearing groove-non-present portion of the portion in which a
hydrodynamic bearing groove is formed during the rotation of the impeller
21 is in the range of 1.5 to 2.5.

[0150]As described above, since the hydrodynamic bearing groove 71 is so
constructed that the value relating to a groove width ratio s
(s=B0/B) is in the range of 0.6 to 0.8 and that the value relating
to a groove depth ratio a (a=h1/h2) is in the range of 1.5 to 2.5, the
hydrodynamic bearing groove 71 is wider and shallower than a logarithmic
groove for hydrodynamic bearing having the same number of grooves. Thus
the hydrodynamic bearing groove 38 generates a less amount of hemolysis.

[0151]A centrifugal blood pump apparatus according to another embodiment
of the present invention is described below.

[0152]FIG. 23 is a front view showing a blood pump apparatus according to
another embodiment of the present invention. FIG. 24 is a vertical
sectional view showing the blood pump apparatus shown in FIG. 23. FIG. 25
is a sectional view, taken along a line F-F in FIG. 23, showing the
centrifugal blood pump apparatus. FIG. 26 is a bottom view showing the
centrifugal blood pump apparatus shown in FIG. 23. A plan view of the
centrifugal blood pump apparatus according to the embodiment shown in
FIG. 23 is the same as the plan view shown in FIG. 18.

[0153]A pump apparatus 150 of this embodiment is different from the pump
apparatus 100 of the above-described embodiment in only the mechanism of
the impeller rotational torque generation section 3. The impeller
rotational torque generation section 3 of the pump apparatus 150 does not
have a rotor, but is of a type of driving the impeller directly. In the
pump apparatus 150 of this embodiment, the impeller 21 rotates without
contacting the inner surface of the housing 20 by a pressure generated by
the hydrodynamic bearing groove 38 when the impeller 21 rotates. In
description which is described below, constructions different from those
of the above-described embodiments are described. The mode of each of a
sensor 45, grooves 38, 71 for hydrodynamic bearing, the control unit 6 is
the same as that of the above-described embodiments.

[0154]As shown in FIGS. 24 and 26, the impeller rotational torque
generation section 3 of the pump apparatus 150 has a plurality of stator
coils 61 accommodated in the housing 20. The stator coils 61 are disposed
along a circumference at equiangular intervals around the axis thereof.
More specifically, six stator coils 61 are used. Multilayer stator coils
are used as the stator coils 61. A rotating magnetic field is generated
by switching the direction current flowing through each stator coil 61.
The impeller is attracted to the rotor by the rotating magnetic field and
rotates.

[0155]As shown in FIG. 25, a plurality (for example, 6 to 12) of the
magnetic materials 25 (for example, permanent magnet, follower magnet) is
embedded in the impeller 21. In the embodiment, the magnetic, materials
25 are embedded in the lower shroud 27. The stator coils 61 provided in
the rotational torque generation section 3 attracts the magnetic material
25 embedded in the impeller toward the side opposite to the side where
the blood inlet port 22 is disposed. In this operation, the magnetic
materials 25 couple to the operation of the stator coils 61 and transmit
the rotational torque from the rotational torque generation section 3 to
the impeller 21.

[0156]The magnetic coupling, to be described later, between the impeller
21 and the stator rotor 61 is ensured by embedding a plurality of the
magnetic materials 25 (permanent magnet) in the impeller 21. It is
preferable that each of the magnetic materials is approximately
trapezoidal. The magnetic materials 25 are ring-shaped or plate-shaped.
It is preferable that the number and arrangement mode of the magnetic
materials 25 correspond to those of the stator coils 61. The magnetic
materials 25 are disposed circumferentially at equiangular intervals
around the axis of the impeller in such a way that positive and negative
poles thereof alternate with each other.

[0157]In the centrifugal blood pump apparatus of the embodiment, the
above-described peripheral configuration of the hydrodynamic bearing
groove is not limited to the above-described one. For example, it is
possible to adopt the logarithmic spiral groove as shown in FIG. 15.